Mitochondria are devoid of poly(ADP‐ribose)polymerase‐1, but harbor its product oligo(ADP‐ribose)

Abstract

There are conflicting data about localization of poly(ADP-ribose)polymerase-1 and its product poly(ADP-ribose) in mitochondria. To finally clarify the discussion, we investigated with biochemical and cell biological methods the potential presence of poly(ADP-ribose) polymerase-1 in these organelles. Our data show that endogenous and overexpressed poly(ADP-ribose)polymerase 1 is only localized to the nucleus with a clear exclusion of cytosolic compartments. In addition, highly purified mitochondria devoid of nuclear contaminations do not contain poly(ADP-ribose)polymerase-1. Although no poly (ADP-ribose)polymerase-1 enzyme is detectable in mitochondria, a shorter variant of its product poly(ADP-ribose) is present, associated specifically with a small subset of mitochondrial proteins as revealed by immunoprecipitation and protein fingerprint analysis. These proteins are located at key-points of the Krebs-cycle, are chaperones involved in mitochondrial functionality and quality-control, and are RNA-binding proteins important for transcript stability, respectively. Of note, despite the fact that especially poly(ADP-ribose) polymerase-1 is its own major target for modification, we could not detect this enzyme by mass spectrometry in these organelles. These data suggests a new way of targeted nuclear-mitochondrial signaling, mediated by nuclear poly (ADP-ribosyl)ation dependent on poly(ADP-ribose)polymerase-1.

The Role of Poly(ADP-ribose) Polymerase 1 in Nuclear and Mitochondrial Base Excision Repair

“…A study exploring the localization of PARG in mouse cortical neurons, using the same major experiments for determining subcellular localization, only saw PARP-1 in the nucleus as well [71]. Similar experiments were performed on HeLaS3 and HEK293 cells [72], and also saw no PARP-1 in mitochondria or cytosol, but did observe oligo-ADP-ribose in mitochondria. More recently, it was shown that mitochondrial PARylation did not decrease in U2OS cells treated with inhibitors specific for PARP-1/2, and that U2OS PARP-1 knockout cells showed an increase in mitochondrial PARylation relative to the control [73].…”

Mitochondrial PARP1 regulates NAD+-dependent poly ADP-ribosylation of mitochondrial nucleoids

“…However, there has been a lack of direct evidence, which has led to much skepticism about mtPARP1. Some studies claim that mitochondria are completely devoid of PARP1, that PARylated proteins enter mitochondria 52 or that mitochondria harbor enzymes other than PARP1 with ADP-ribosyltransferase activity 11 . On the other hand, some studies report the involvement of PARP1 in mtDNA metabolism, demonstrating direct interactions between PARP1 and mtDNA for mtDNA maintenance 9 and repair 53 .…”

Specific and shared biological functions of PARP2 – is PARP2 really a lil’ brother of PARP1?

“…170). Importantly, the pathways stemming from oxidative stress-induced PARP2 activation were identified in plants ( Refs 184,185) 197). PARP2 impacts on lipid metabolism in the white adipose tissue (Ref.…”

“…Interestingly, in Arabidopsis PARP2 is present in the mitochondria (Ref. 196) that is an interesting phenomenon, as in mammalian cells no PARylating activity was identified in the mitochondria (Refs 165, 197).…”

“…As mentioned earlier, the deletion of PARP2 induces SIRT1 expression and SIRT1 activity. Through that pathway, the deletion of PARP2 induces mitochondrial biogenesis in metabolically 197). PARP2 impacts on lipid metabolism in the white adipose tissue (Ref.…”